“The EU is by far the UK’s biggest trading partner. EU countries buy 44% of everything we sell abroad, from cars to insurance.”
About 44% of UK exports in goods and services went to other countries in the EU in 2014. That compares to about 21% to countries in the Americas, 19% to Asian countries, 11% to non-EU European countries, and 5% to everywhere else in the world.
That share has been declining, as exports to other countries have been increasing at a faster rate.
It’s sometimes argued that these statistics overstate the proportion of UK exports that go to the EU, as a lot of goods pass through ports like Rotterdam before being shipped to a final destination outside the EU. Both the Office for National Statistics and the government's review of our EU membership have concluded that it's hard to quantify the extent of this ‘Rotterdam effect’ or establish whether it's a serious problem for the statistics.
It’s not clear what would happen to this trade if the UK votes to leave the EU. If the UK leaves the EU, the future rules on trade would depend on what kind of agreement, if any, the UK reaches with the EU after its departure.
Update 18 May 2016
We clarified that 5% of the UK's exports go to areas of the world not previously included in our breakdown.